[dahart]

Try to write Floyd-Steinberg dithering on the GPU. ;)

I've learned a lot by trying to port branchy code & recursive algorithms to the GPU, then trying to figure out why the performance is terrible and how to fix it. Specifically, I learned a bunch trying to write custom primitive intersection shaders for OptiX (https://developer.nvidia.com/optix).

I like ShaderToy as well, but since it's so easy and hides the abstractions from you, you have to really look around for the amazing tricks other people there have used. Also write code that slows down your GPU and then improve it. Just getting pretty things to render and/or writing shaders that start out at 60fps won't help you learn as fast.

[pjc50]

Yeah, an algorithm that makes every pixel dependent on the previous one is pretty much the worst-case for GPU computation :)